LAUSR

Background: Breast cancer (BC) is the most frequent cancer and the leading cause of cancer-related death in women. The French National Cancer Institute has created a national cancer cohort to promote cancer research and improve our understanding of cancer using the National Health Data System (SNDS). This cohort amalgamates all cancer sites, with no detailed separate data for early BC. Objectives: We describe the French Early Breast Cancer Cohort (FRESH). Methods: All French women aged 18 years or over, with early-stage BC newly diagnosed between January 1, 2011 and December 31, 2017, treated by surgery and registered in the general health insurance coverage plan were included in the cohort. Patients with suspected locoregional or distant metastases at diagnosis were excluded. BC treatments (surgery, chemotherapy, targeted therapy, radiotherapy, endocrine therapy), and diagnostic procedures (biopsy, cytology, imaging) were extracted from hospital discharge reports, outpatient care notes or pharmacy drug delivery data. BC subtype was inferred from the treatments received. Results: We included 235,368 patients with early BC in the cohort (median age: 60 years). BC subtype distribution was as follows: luminal (80.2%), triple-negative (TNBC, 9.5%); HER2+ (10.3%), or unidentifiable (n=44,388, 18.9% of the cohort). Most patients underwent radiotherapy (n=200,685, 85.3%) and endocrine therapy (n=165,655, 70.4%), and 38.3% (n=90,252) received chemotherapy. Treatments and care pathways are described. Conclusion: The FRESH Cohort is an unprecedented population-based resource facilitating future large-scale real-life studies aiming to improve care pathways and quality of care for BC patients.